Numerous one-way valves for discharging a liquid out of a container are known. For instance, EP 1 499 538 B1 discloses a one-way valve in which a valve seat is inserted into the container neck covered by a valve body of elastic material. Upon exertion of pressure on the container the contents of the container flows between a projection of the valve seat and the valve body through an exit opening of an outer cap covering said one-way valve.